Add Go statusline implementation

Replace shell-based statusline with native Go for ~4x speedup.
Parses JSON natively, detects git status, checks gitea process,
and formats colored output with proper terminal width handling.

.gitignore

@@ -0,0 +1,45 @@
+/statusline
+/bin
+
+# Created by https://gitignore.kjanat.com/api/go,linux
+# Edit at https://gitignore.kjanat.com?templates=go,linux
+
+### Go ###
+# If you prefer the allow list template instead of the deny list, see community template:
+# https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
+#
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/
+
+# Go workspace file
+go.work
+
+### Linux ###
+*~
+
+# temporary files which can be created if a process still has a handle open of a deleted file
+.fuse_hidden*
+
+# KDE directory preferences
+.directory
+
+# Linux trash folder which might appear on any partition or disk
+.Trash-*
+
+# .nfs files are created when an open file is removed but is still being accessed
+.nfs*
+
+# End of https://gitignore.kjanat.com/api/go,linux

go.mod

@@ -1,3 +1,5 @@
 module github.com/kjanat/claude-statusline
 
 go 1.24.11
+
+require golang.org/x/sys v0.39.0

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
+golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=

main.go

@@ -0,0 +1,202 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+const statuslineWidthOffset = 7
+
+// Input JSON structure from Claude Code
+type StatusInput struct {
+	Model struct {
+		DisplayName string `json:"display_name"`
+	} `json:"model"`
+	Workspace struct {
+		CurrentDir string `json:"current_dir"`
+	} `json:"workspace"`
+	ContextWindow struct {
+		ContextWindowSize int `json:"context_window_size"`
+		CurrentUsage      *struct {
+			InputTokens          int `json:"input_tokens"`
+			CacheCreationTokens  int `json:"cache_creation_input_tokens"`
+			CacheReadInputTokens int `json:"cache_read_input_tokens"`
+		} `json:"current_usage"`
+	} `json:"context_window"`
+}
+
+// ANSI color codes
+const (
+	reset     = "\033[0m"
+	bold      = "\033[1m"
+	red       = "\033[31m"
+	green     = "\033[32m"
+	yellow    = "\033[33m"
+	magenta   = "\033[35m"
+	cyan      = "\033[36m"
+	boldGreen = "\033[1;32m"
+)
+
+func main() {
+	// Read JSON from stdin
+	reader := bufio.NewReader(os.Stdin)
+	var input strings.Builder
+	for {
+		line, err := reader.ReadString('\n')
+		input.WriteString(line)
+		if err != nil {
+			break
+		}
+	}
+
+	var data StatusInput
+	if err := json.Unmarshal([]byte(input.String()), &data); err != nil {
+		fmt.Fprintf(os.Stderr, "Error parsing JSON: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Calculate context info
+	contextInfo := formatContextInfo(data.ContextWindow.ContextWindowSize, data.ContextWindow.CurrentUsage)
+
+	// Get directory name
+	dirName := filepath.Base(data.Workspace.CurrentDir)
+
+	// Check gitea status
+	giteaStatus := getGiteaStatus()
+
+	// Get git info
+	gitInfo := getGitInfo(data.Workspace.CurrentDir)
+
+	// Build left part
+	left := fmt.Sprintf("%s %s%s%s %s➜%s %s%s%s%s",
+		giteaStatus,
+		magenta, data.Model.DisplayName, reset,
+		boldGreen, reset,
+		cyan, dirName, reset,
+		gitInfo)
+
+	// Build right part
+	right := fmt.Sprintf("%s%s%s", yellow, contextInfo, reset)
+
+	// Calculate visible lengths (strip ANSI)
+	leftVisible := stripANSI(left)
+	rightVisible := stripANSI(right)
+
+	// Get terminal width
+	termWidth := getTerminalWidth() - statuslineWidthOffset
+
+	// Calculate padding
+	padding := termWidth - len(leftVisible) - len(rightVisible)
+	if padding < 1 {
+		padding = 1
+	}
+
+	// Output with padding
+	fmt.Printf("%s%s%s", left, strings.Repeat(" ", padding), right)
+}
+
+func formatContextInfo(contextSize int, usage *struct {
+	InputTokens          int `json:"input_tokens"`
+	CacheCreationTokens  int `json:"cache_creation_input_tokens"`
+	CacheReadInputTokens int `json:"cache_read_input_tokens"`
+}) string {
+	totalK := contextSize / 1000
+
+	if usage == nil {
+		return fmt.Sprintf("0/%dk", totalK)
+	}
+
+	currentTokens := usage.InputTokens + usage.CacheCreationTokens + usage.CacheReadInputTokens
+	currentK := currentTokens / 1000
+	return fmt.Sprintf("%dk/%dk", currentK, totalK)
+}
+
+func getGiteaStatus() string {
+	// Check if gitea process is running using pgrep
+	cmd := exec.Command("pgrep", "-x", "gitea")
+	if err := cmd.Run(); err == nil {
+		return green + "●" + reset
+	}
+	return red + "●" + reset
+}
+
+func getGitInfo(cwd string) string {
+	// Change to the directory
+	oldDir, _ := os.Getwd()
+	if err := os.Chdir(cwd); err != nil {
+		return ""
+	}
+	defer os.Chdir(oldDir)
+
+	// Check if we're in a git repo
+	cmd := exec.Command("git", "rev-parse", "--git-dir")
+	cmd.Stderr = nil
+	if err := cmd.Run(); err != nil {
+		return ""
+	}
+
+	// Get branch name
+	branch := ""
+	cmd = exec.Command("git", "symbolic-ref", "--short", "HEAD")
+	cmd.Stderr = nil
+	if out, err := cmd.Output(); err == nil {
+		branch = strings.TrimSpace(string(out))
+	} else {
+		// Fallback to short SHA
+		cmd = exec.Command("git", "rev-parse", "--short", "HEAD")
+		cmd.Stderr = nil
+		if out, err := cmd.Output(); err == nil {
+			branch = strings.TrimSpace(string(out))
+		}
+	}
+
+	if branch == "" {
+		return ""
+	}
+
+	// Check if working tree is dirty
+	isDirty := false
+
+	// Check unstaged changes
+	cmd = exec.Command("git", "diff", "--no-ext-diff", "--quiet", "--exit-code", "--no-optional-locks")
+	cmd.Stderr = nil
+	if err := cmd.Run(); err != nil {
+		isDirty = true
+	}
+
+	// Check staged changes
+	if !isDirty {
+		cmd = exec.Command("git", "diff-index", "--cached", "--quiet", "HEAD", "--no-optional-locks")
+		cmd.Stderr = nil
+		if err := cmd.Run(); err != nil {
+			isDirty = true
+		}
+	}
+
+	if isDirty {
+		return fmt.Sprintf(" git:(%s) ✗", branch)
+	}
+	return fmt.Sprintf(" git:(%s)", branch)
+}
+
+func getTerminalWidth() int {
+	ws, err := unix.IoctlGetWinsize(int(os.Stdout.Fd()), unix.TIOCGWINSZ)
+	if err != nil {
+		return 80
+	}
+	return int(ws.Col)
+}
+
+var ansiRegex = regexp.MustCompile(`\x1b\[[0-9;]*m`)
+
+func stripANSI(s string) string {
+	return ansiRegex.ReplaceAllString(s, "")
+}